1. Field of the Invention
The present invention relates to a metal-resin bond grindstone for use in ELID grinding, and a method for manufacturing the same.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 1-188266 by the same applicant as in the present application discloses a method and an apparatus for carrying out electrolytic dressing on a conductive grindstone, i.e., dressing in an electrolytic manner a metal bond grindstone, to which a voltage is applied, such as a cast iron fiber bond diamond grindstone or a similar conductive grindstone. The publication reports a success in performing specular grinding on electronic semiconductor materials such as silicon. Besides, the present applicant has developed and announced an apparatus and a method called the Electrolytic In-process Dressing method (hereinafter referred to as the ELID method)(RIKEN Symposium "The Latest Technological Trend of Specular Grinding" held on Mar. 3rd, 1991).
The ELID method uses an apparatus which comprises a grindstone having a contact surface with a work-piece, electrodes facing the grindstone with a distance therebetween, nozzles for allowing a conductive liquid to flow between the grindstone and the electrodes, and a voltage application device (comprising a power supply and a feeder circuit) for applying a voltage between the grindstone and the electrodes, and the voltage is applied between the grindstone and the electrodes while the conductive liquid is allowed to flow between the grindstone and the electrodes, thereby performing the electrolytic dressing on the grindstone.
Since the ELID method can use fine abrasive grains without loading by virtue of the electrolytic dressing, it can thus give an extremely good worked surface such as a mirror surface by the use of the finer abrasive grains. The ELID method can therefore maintain an excellent cutting function of the grindstone ranging from high-performance grinding through mirror finish grinding, and thus the application of the ELID method to various fields of the grinding can be expected.
The above-mentioned ELID method, however, uses an inelastic hard metal as a grindstone bond, so that there are problems of "chipping" of a work-piece during the grinding and "scratches" of the work-piece by the chips. Accordingly, even by the above-mentioned ELID grinding, an obtained mirror surface merely has a Rmax of about 18 to 20, and it has a problem that the higher quality mirror surface cannot be obtained.
Therefore, to obtain the higher quality mirror surface, the conventional methods must use another method such as polishing together, but in such a case, there are problems, such as that the high-performance grinding effect of the ELID grinding is reduced and much time is taken to complete the whole processing.
To solve the above problems, the present inventors have earlier contrived a method and an apparatus in which abrasive grains are mixed with a bonding material comprising metal powder and a resin; the mixture is heated and melted to form a conductive grindstone; and the thus formed conductive grindstone is used to carry out ELID grinding (see Japanese Patent Application Laid-Open No. 7-285071). By this method and the related apparatus, it has been made possible to obtain a high-quality mirror surface with an Rmax value of about 13-15 nm which is not liable to have chippings or scratches.
The above-mentioned conductive grindstone (hereinafter referred to as the metal-resin bond grindstone) which mixes a grindstone and a bonding material comprising metal powder and a resin, gives higher quality of mirror surfaces as the grain diameter of the metal powder is smaller. If, however, the grain diameter of the metal powder is reduced to about 1 .mu.m, the thus made metal-resin bond grindstone has higher electric resistivity and so loses a conductivity essential for ELID grinding, thus making the grinding impossible. With this problem, the ELID methods using the conventional grindstones cannot obtain high quality mirror surfaces with an Rmax value of 10 nm or less.